To titty fuck butt cheeks is to take your member and take your partner and lube up the butt cheeks and squezze them together and begin to thrust your member inbetween them simulating the feeling of a pussy.

Mosley said to Mike, "If you dont knock it off im going to titty fuck your butt cheeks!!!" or "Hunny I'm on my period and you know I don't like to do it in the butt. Well can I titty fuck your butt cheeks?"